Distance Measurement for Building Automation Devices with Wireless Data Communications

ABSTRACT

In a building environment, a distance associated with a building automation device is determined as a function of an interval or an inserted time delay between a wireless transmission of a signal and wireless reception of another signal. For example, a two-way communication is provided with an automatic interval or a desired time delay inserted before responding to a received transmission. By using two-way transmissions, the building automation devices may be free of clock synchronization. Acoustic signals may be used in a building environment to determine a distance. The building automation device may also use radio frequency information for communicating with other devices.

RELATED APPLICATION

The present patent document is a continuation-in-part of applicationSer. No. 10/937,078, filed Sep. 9, 2004 (now U.S. Published ApplicationNo. 2006/0049976), which is hereby incorporated by reference.

BACKGROUND

The present invention relates to wireless building automation. Inparticular, distance measurement is provided for locating or determininga position of a building automation device with wireless datacommunications.

Building automation devices are positioned throughout a building. Forexample, a temperature sensor or thermostat is positioned on a wall in aroom and a corresponding actuator is positioned above a ceiling forcontrolling airflow, heating or cooling. As another example, a motionsensor is positioned on a ceiling for actuating a light controlled by aballast balance above the ceiling. Security, fire, heating, ventilation,air conditioning (HVAC) or other networks of devices automate buildingcontrol. The relative positions of different devices or the relativepositions of devices with respect to the layout of a building or roomsmay be used to better optimize the automation. To determine thedifferent positions, a blueprint or map is generated of the automationsystem. The devices are located manually, and corresponding associationtables between devices are created. Manual mapping may be inaccurate.When a device malfunctions, inaccurate mapping or no mapping makeslocating a device difficult, particularly where the device is locatedout of site above a ceiling or in a wall. Adding visual indicationsidentifying a location of an otherwise out of site device isunaesthetic. Manually locating devices for replacement may be timeconsuming and costly.

BRIEF SUMMARY

By way of introduction, the preferred embodiments described belowinclude methods and systems for determining distances for buildingautomation components. In a building environment, various features aloneor in combination assist in distance determination. A distanceassociated with a building automation device is determined as a functionof an interval between a wireless transmission of a signal and wirelessreception of another signal. For example, a two-way communication isprovided with an interval of known time inserted before responding to areceived transmission. The interval is based on a time delay, a responsetime, or other delay. By using two-way transmissions, the buildingautomation devices may be free of clock synchronization. Acousticsignals may be used in a building environment to determine a distance.The building automation device may also use radio frequency informationfor communicating with other devices.

In a first aspect, a method is provided for determining a distance for abuilding automation device. A first signal is wirelessly transmittedfrom the building automation device within a building. A second signalis wirelessly received at the building automation device within thebuilding. A distance associated with the building automation device isdetermined as a function of a time-of-flight for the first and secondsignals and a delay of known time interval.

In a second aspect, a system is provided for determining a distance forbuilding automation components. A first building automation device has afirst wireless transmitter, a first wireless receiver and a firstprocessor. A second building automation device has a second wirelesstransmitter, a second wireless receiver and a second processor. Thefirst wireless transmitter is operable to transmit a first signal, thesecond wireless receiver is operable to receive the first signal, andthe second wireless transmitter is operable to transmit a second signalin response to reception of the first signal and after an interval, thefirst wireless receiver operable to receive the second signal, and thefirst processor, second processor or a third processor is operable todetermine a distance between the first and second building automationdevices as a function of the interval and time from transmission of thefirst signal to reception of the second signal.

In a third aspect, a method is provided for determining a distance for abuilding automation device. A first device measures a first time from afirst data marker in a first wireless message to a second data markergenerated by the first device. A second device measures a second timefrom a third data marker in a second wireless message to a fourth datamarker generated by the second device. A time-of-flight is determined asa function of subtracting the second time from the first time anddividing a result of the subtraction by two.

The present invention is defined by the following claims, and nothing inthis section should be taken as a limitation on those claims. Furtheraspects and advantages of the invention of the invention are discussedbelow in conjunction with the preferred embodiments and may be laterclaimed independently or in combination.

BRIEF DESCRIPTION OF THE DRAWINGS

The components in the figures are not necessarily to scale, emphasisinstead being placed upon illustrating the principles of the invention.Moreover, in the figures, like reference numerals designatecorresponding parts throughout the different views.

FIG. 1 is a block diagram of one embodiment of a building automationdevice;

FIG. 2 is a top plan view of one embodiment of a network of buildingautomation devices; and

FIG. 3 is a flow chart diagram of one embodiment of a method fordetermining a distance for building automation components.

DETAILED DESCRIPTION OF THE DRAWINGS AND PRESENTLY PREFERRED EMBODIMENTS

In building automation systems, the location or coordinate position ofthe various devices is determined using a distance measurement. Byproviding a plurality of different distance measurements from apredetermined or known reference point, the position or coordinatelocation may be triangulated. As a location of each device within anetwork of devices is identified, further locations of other devicesrelative to the now known location may be determined. The relativelocation of different devices may allow for pairing or relating devicesinto groups, such as a thermostat related to an actuator and acontroller. In addition to or as an alternative to identifying aposition or location in two- or three-dimensions, a distance may be usedfor determining a signal strength or other purposes.

Time-of-flight information of a wireless signal is used to identify adistance. Radio frequency, acoustic, combinations thereof or other typesof signals are used. For example, a timing packet is transmitted usingultrasound energy. The packet is received at a different device. Afterwaiting a particular known time interval, the different device transmitsthe packet or other information acoustically or using a radio frequencysignal back to the source device. The interval may be based on a timerat the different device, an interval associated with substantiallyimmediate response, an interval set by a communications or otherprotocol, a number of clock cycles, a count, a count-down time or otherinterval. The source device measures the end-to-end response time toobtain the distance.

FIGS. 1 and 2 show a system for determining a distance for buildingautomation components. FIG. 1 shows a building automation device 10 usedwithin the system. The building automation device includes a sensor oractuator 12, a processor 14, a wireless radio frequency transmitter orreceiver 16, a speaker 18 and a microphone 20. Additional, different orfewer components may be provided. For example, the building automationdevice 10 is free of the speaker 18, the microphone 20, the speaker 18and the microphone 20, the wireless transmitter or receiver 16, and/orthe sensor or actuator 12.

The building automation device 10 is a controller, actuator, sensor orother device in a security, fire, environment control, HVAC, lighting,or other building automation system. As a controller, the buildingautomation device 10 may be free of the sensor or actuator 12. In oneembodiment, the building automation device 10 includes a wiredconnection to one or other devices 10 within the network and is eitherfree of or also includes the wireless radio frequency transmitter orreceiver 16. In yet another embodiment, the building automation deviceis a wireless device free of communications or connections over wires toother remote devices. For example, the building automation device is anyone of the building control system devices, processors or controllersdisclosed in U.S. Patent Application Publication No. 2006/0028997, thedisclosure of which is incorporated herein by reference. A wirelessdevice for one communications route may be wired for anothercommunications route.

The sensor or actuator 12 is a single sensor, multiple sensors, singleactuator, multiple actuators or combinations thereof. As a sensor, thesensor 12 is a temperature, humidity, fire, smoke, occupancy, airquality, gas, CO₂, CO, combinations thereof or other now known or laterdeveloped sensor. Micro-electromechanical or larger sensors may beprovided for sensing any of various environmental conditions. As anactuator, the actuator 12 is a valve, relay, solenoid, speaker, bell,switch, motor, motor starter, damper, pneumatic device, combinationsthereof or other now known or later developed actuating devices forbuilding automation. For example, the actuator 12 is a valve forcontrolling flow of fluid or gas in a pipe. As another example, theactuator 12 is a relay or other electrical control for opening andclosing doors, releasing locks, actuating lights, or starting andstopping motors. Yet another example, the actuator 12 is a solenoid toopen or close a damper, such as for altering airflow.

Where the building automation device 10 is free of the sensor oractuator 12, the device 10 may be a controller. The controller ispositioned at a known or unknown location. As a controller, the buildingautomation device 10 interacts with other building automation devices 10for configuring, coordinating, influencing, controlling, or performingother control or reporting functions.

The processor 14 is a general processor, digital signal processor,application-specific integrated circuit, field programmable gate array,analog circuit, digital circuit, network of processors, combinationsthereof or other now known or later developed device for processing dataand/or controlling operation of the building automation device 10. Theprocessor 16 has a processing power or capability and associated memorycorresponding to the desired operation of the device 10 or a class ofdevices, such as an eight or sixteen bit processor. By minimizingprocessor requirements and associated memory, the cost and powerconsumption of the device 10 may be reduced. Larger or smallerprocessors and associated memories may be used, such as a largerprocessor where the device 10 is operating as a controller.

The processor 14 is operable to cause transmission or reception actionsby the wireless radio frequency transmitter or receiver 16, the speaker18 or the microphone 20. For example, the processor 14 is operable tocause the acoustic speaker 18 to transmit an ultrasound signal. Theprocessor 14 is also operable to cause the microphone 20 to receive anultrasound signal and determine a distance from another device as afunction of the received signal. Alternatively or additionally, theprocessor 14 is operable to cause the wireless radio frequencytransmitter or receiver 16 to transmit data for determining thedistance. Additionally or alternatively, the wireless radio frequencytransmitter 16 transmits a determined distance or distances as well asdata regarding the processes and operation of the sensor or actuator 12.

The wireless radio frequency transmitter and receiver 16 or the speaker18 are alternate wireless transmitters operable to transmit a signal fordistance determination. Similarly, the wireless radio frequency receiver16 and microphone 20 are alternative wireless receivers operable toreceive signals for distance determination.

The wireless radio frequency transmitter or receiver 16 is atransmitter, a receiver or a transceiver. The wireless radio frequencytransceiver 16 operates pursuant to any of various now known or laterdeveloped communications protocols, such as IEEE 802 wirelesscommunications protocols. The wireless radio frequency transceiver 16 isoperable to transmit digital or analog information, such as a carrierwave modulated by digital signals. The wireless transceiver 16 transmitstiming or other distance related information, such as a sinusoidalpulse. The wireless transceiver 16 is operable to receive timing ordistance information, such as a transmitted pulse subjected toattenuation or other environmental alteration. Filters or otherprocesses may be used to remove noise or other undesired information.

In an alternative or additional embodiment, the speaker 18 andmicrophone 20 are used for wirelessly transmitting and receivinginformation for determining a distance. The speaker 18 and microphone 20are an acoustic transducer or transceiver. A piezoelectric ceramic orcomposite piezoelectric, a micro-electromechanical device, such as aflexible membrane or membranes, waveguide, or other now known or laterdeveloped speakers and microphones as separate devices or transceiversmay be used. An array of acoustic transceivers is provided fordirectional processing, such as determining an angle for transmissionsor receptions. An array may alternatively or additionally be used forgenerating a desired radiation pattern. Alternatively, a single acoustictransceiver is positioned on an outside of the device 10 to maximize theradiation pattern. The speaker 18 and microphone 20 are sized and shapedfor operation at ultrasound frequencies, such as 20 KHz or higher.Frequencies in the megahertz range, such as 1 to 20 MHz, lowerfrequencies, or audible frequencies may be used.

The processor 14 is operable to control the acoustic transceiver fordistance determination operation. For example, the processor 14 causesthe acoustic transceiver 18, 20 to transmit an acoustic pulse, such as asinusoidal, bipolar or unipolar pulse. Any of various pulse lengths maybe used, such as single cycle or multiple cycle pulses. A desiredtransmit amplitude is provided, such as associated with transmitting theacoustic energy over a distance of 10-20 meters. The transmit amplitudemay be adjustable. Depending on the building environment, such as anenclosed office building, the transmit amplitude may be set forreception by a likely plurality of other devices within a restrictedspace. The processor 14 is also operable to process receivedinformation, such as identifying a zero crossing, amplitude, datacontent or other characteristic of received acoustic energy.

Where a wireless radio frequency transceiver 16 is provided with thespeaker 18 and microphone 20, the wireless radio frequency transceiver16 is used to control operation of the processor 14 and distancemeasurements using the acoustic transceiver 18, 20. Control signals arereceived wirelessly using the wireless radio frequency transceiver 16.The control signals coordinate distance determination among variousdevices or for a specific device. For example, the control signalsindicate when and what type of a test signal or actual measurementsignal is transmitted for distance determination. As another example,control signals from the wireless transceiver 16 instruct the processor18 to act to receive or not act to receive acoustic transmission fromone or other different devices. Control signals may be used to alter aninsert time delay, set signal strength, select signal processing,establish communications protocol, provide the delay information,provide time-of-flight information or control another process.

The processor 14 is also operable to determine a distance betweenbuilding automation devices 10 or the building automation device 10 andanother device. The distance is determined by the same processor usedfor initiating the transmission of a signal, the processor that receivesa first transmitted signal, or a processor remote from either of thedevices that transmitted the distance signal or received the distancesignal for determining time-of-flight. In one embodiment, the processor14 uses time-of-flight information to determine the distance. A one-waytime-of-flight associated with transmitting from one component andreception at another component may be used. Alternatively oradditionally, a two-way time-of-flight is used where one componenttransmits a signal, another device receives the signal and responsivelytransmits another signal and the originating device receives theresponsively transmitted signal.

To distinguish between echoes of radio frequency or acoustic signals ina building environment, the processor 14 identifies the first to arrivesignals. For example, the processor 14 is configured for performingdistance determination functions. A receiver is monitored. A firstsignal having a sufficient signal strength is selected as the signal ofinterest. Echoes have a longer distance to travel, so are laterarriving. Coding or other techniques may be used to indicate a signal ofinterest as compared to noise or other signals. Alternatively, anamplitude threshold is used to indicate a signal of interest as comparedto noise.

For more accurate time-of-flight determination, a characteristic of thereceived signal is analyzed to identify a time at which a portion of thesignal was received. A first, second or other zero crossing isidentified in one embodiment for higher resolution timing. Zero crossinginformation may be interpolated from samples associated with a zerocrossing. Each receive signal in a two-way response system is identifiedusing a same portion or different portions of the signal, such as a samezero crossing.

Another characteristic of the signal is a data marker. The data markermay be part of a data stream, such as a digital or analog modulatedcarrier wave or the demodulated data. The timing of transmission and/orreception is determined by the modulation, demodulation or otherdetection of particular data. For example, a data marker for determiningdistance is used. A packet or other group of data is inserted into thedata stream or makes up the data stream. The packet contains the datamarker. The insertion of the marker into the data stream and detectionat modulation or other passing or generating points is used to determinea transmit time, start a counter or begin a count down. The marker isdetected to determine reception time, such as detecting the data beforeor after demodulation. Identification of the marker is a trigger for thetiming of reception and/or transmission.

Other data markers may be used, such as a frame or packet marker. Theframe marker may be provided for each transmission and/or data packet.For example, a start of frame delimiter is provided in every frame ofdata at a set location within the frame. The processors 14 of the sourceand destination building automation devices 10 detect when the markerpasses into and/or out of the wireless communications channel (e.g., thetransceiver 16). The data marker is placed in one or more frames of datapursuant to a protocol, such as a communications protocol (e.g., IEEE802 or ZigBee networking). For example, a start of frame delimiter ispositioned in every frame of data pursuant to a standard protocol.Alternatively, the data marker is placed pursuant to privatecommunications format. Markers provided only in a subset of the framesmay be used. Different characteristics may be used for differentsignals.

The signal is sampled to identify information to the desired accuracy. A12 GHz sampling may resolve radio frequency information to an inch, a 6GHz sampling frequency may resolve information to two inches, a 1 GHzsampling frequency may resolve information to one foot, and a 500 MHzsampling frequency may resolve information to two feet. Other relativefrequencies and associated resolutions may be provided. Sound travels atapproximately 1.1 feet per millisecond, so may be sampled at a lesserfrequency while still providing high accuracy at an inch, foot or yardlevel.

For data, the signal sampling corresponds to a data rate. Greater datarates provide for greater possible accuracy for distance determination.In one embodiment, a timer is used to count down to determine theinterval between reception and transmission or the length of timebetween transmission and reception. In another embodiment, a counter isprovided to determine a number of clock cycles, data symbols or otherperiodic triggers between transmission and reception events. The timeror counter may be part of the processor 14 or a separate component ofthe building automation device 10. The timer or counter is sufficientlylarge to operate in the desired distance range given the type ofwireless transmission. For example, a counter is wide (e.g., multiplebits wide) to count sufficiently high given an expected two-waycommunications and any interval at the sampling rate. For radiofrequency wireless, the counter may count up to 2 to the 23^(rd) or24^(th) power. Larger or smaller counts may be possible.

For two-way response, the processor 14 is operable to insert a timedelay, delay interval or other interval. Insertion may be purposeful orthe result of hardware and/or software based capability or settings. Forexample, the processor 14 is part of a device 10 that responds to atransmitted signal with an additional transmitted signal. The processor14 identifies a particular portion of the signal or a general time whenthe signal is received. The processor 14 then delays a set time period,such a time period associated with providing a sufficient time for theprocessor 14 and the device 10 to react, before generating a transmitsignal in response. The time delay may be implemented by starting acountdown timer, but may be implemented by counting clock cycles or datasymbols up to a set or predetermined number or using time stamps. Theinterval or set time delay may be preprogrammed, such as programmedduring manufacture, programmed after installation through wireless radiofrequency control signals, established as part of a communicationsprotocol, random, a limitation of the hardware or software or manuallyconfigured.

In one embodiment, the interval is associated with an immediateresponse. By detecting the signal or data and generating a correspondingresponse (e.g., determining an appropriate transmission), the buildingautomation device 10 or the processor 14 provides an immediate responsewithout an interval or the interval is smaller, similar or larger thanpropagation time. For example, a communications protocol may provide fora specific immediate response time, such as 8 symbols. As anotherexample, the hardware or software may limit the response time, causingan interval. Non-immediate responses may be provided, such as providingfor larger or smaller intervals. The interval is known or set, or may bedetermined based on counted time to perform an action or a time stamp.Counting clock cycles or other cyclical events, time stamps, or acountdown timer may be used to determine or provide the interval.

The processor 14 associated with determining the distance determines thedistance as a function of the time-of-flight with or without the settime delay or other interval. The set time delay or interval iscommunicated or previously programmed into the processor 14. The settime delay or interval is subtracted from the roundtrip time calculatedby the processor 14. The roundtrip time is then divided by two andmultiplied by the speed of sound and/or light depending on the type ofsignal. The result provides a distance.

Alternative distance measurement may performed by having a first devicestart a first timer when a first data marker is transmitted from thefirst device and stop the timer when a second data marker in a secondmessage from a second device is received at the first device. The seconddevice starts a second timer when the first marker of the first messageis received at the second device and stops the timer when the secondmarker of the second message is transmitted from the second device. Thefirst, second, or a third processor subtracts the time from the firsttimer from the value of the second timer then divides that value by twoto determine the time of flight.

The transmitted signal may include coding information indicating a timeof transmission. The received signal may then be used to determinetime-of-flight. Where synchronization between devices is unavailable, atwo-way distance determination may avoid inaccuracies due tounsynchronized clocks. Alternatively, synchronization is providedallowing one-way or two-way determination of distance. Thesynchronization is provided over a common clock or heartbeat signalprovided wirelessly or through a wired connection to the device 10.

To minimize the effects of interference, both acoustic and radiofrequency distance determinations may be performed at same or differenttimes. Other mechanisms to minimize the effects of noise may beprovided, such only accepting distances less than a certain value, suchas 10 meters or other value associated with a likely relationshipbetween two devices 10. The threshold may vary as a function of the typeof device 10.

FIG. 2 shows a network of devices 10 for operating with one or morecontrollers 22 within a building 24. The plurality of devices 10 arespaced apart throughout the building 24, such as one or more devices 10being put in each of or a number of rooms within the building 24.Different spacings may be provided. While one controller 22 is shown, aplurality of controllers 22 may be provided in other embodiments.Additional, different or fewer devices 10 and controllers 22 may beprovided. Different distributions of the devices 10 may be provided.While shown as a single floor of a building 24, the network of devices10 and controllers 22 may be distributed over multiple floors, a portionof the floor, a single room, a house or other building 24. In oneembodiment, the network of devices 10 and controllers 22 is a networkfor wireless building automation or control, such as disclosed in U.S.Application Publication No. 2006/0028997. Other wireless or wirednetworks may be provided in alternative embodiments.

The various devices 10 are of a same configuration or differentconfiguration than each other. For example, some of the devices 10correspond to sensor arrangements while other devices 10 correspond toactuator arrangements. The same or different communications devices,such as the transceiver 16 or the acoustic transceiver 18, 20, areprovided for each of the devices 10. Alternatively, differentcommunications mechanisms and/or protocols are provided for differentgroups of the devices 10. The devices 10 may operate in an integratedmanner for implementing one or multiple types of building automationcontrol. Alternatively, different networks are provided for differenttypes of building automation, such as security, HVAC and fire systems.

The controller 22 is the device 10 without a sensor or actuator 12.Alternatively, the controller 22 includes the sensor or actuator 12. Thecontroller 22 is operable to wirelessly communicate with a plurality ofspaced apart building automation devices 10. For example, acoustic orradio frequency communications are provided. Distances between any givendevice 22 and another device may be determined without information orcontrol from the controller 22. Alternatively, the controller 22triggers, controls or alters the distance determination between twogiven devices 10. In other embodiments, the distance associated with thedevice 10 is performed relative to the controller 22, such as where theposition of the controller 22 is known.

In one example embodiment of the controller 22 controlling determinationof the distance, the controller 22 is operable to cause one of thedevices to transmit a test-ranging signal. Information is received fromother adjacent devices indicating reception or lack of reception ofsufficient signal strength. The power of subsequent ranging signals froma given device 10 may be increased and/or devices operable to receivethe test-ranging signal of sufficient strength are assigned to interactwith the device 10 for determining the distance from various locations.The distances from the device 10 acting as a source of the test signalto each of the assigned devices 10 is then determined. The devices 10may be ordered to take turns or act sequentially to determine aplurality of distances associated with each device. Given the variouspossible structures and sources of interference within a building 24,the network control of the distance determination functions may morelikely result in accurate distance measurements rather than distancesbased on echo information. Alternatively, one or more distances is basedon echo information but is sufficiently accurate. Other control schemesor mechanisms may be provided.

Spread spectrum or code phasing may be used for range determination inother embodiments. For example, spread spectrum gold code istransmitted. The received signal is then correlated with a replica codegenerated at the receiver to determine a code phase offset indicating adistance. Other location or range determining signal structures may beused.

Where the device 10 is malfunctioning or in response to a determinedalarm, the speaker 18 generates acoustic information in an audiblefrequency. For example, a chirp is sounded to allow maintenancepersonnel to more easily find a malfunctioning device. As anotherexample, an alarm signal is sounded with the speaker 18 in response to adetected security or safety situation. The device 10 is operable toimplement the generation of audible sound without information from otherdevices 10 or the controller 22. Alternatively, the speaker 18 isactivated in response to control signals from the controller 22 orinformation from another device 10. Similarly, the microphone 20 may beused for other functions than range determination. For example, amicrophone 20 is used for communication with building securitypersonnel.

FIG. 3 shows one embodiment of a method for determining a distance for abuilding automation device. The method is implemented using the devices10 shown in FIG. 1, the network of devices 10 and controllers 22 shownin FIG. 2 or different devices or networks. Different, additional orfewer acts may be provided than shown in FIG. 3. For example, acts 44,46 and 48 are performed without the previous acts. As another example,acts 38 through 48 are performed without the previous acts. As anotherexample, the acts shown in FIG. 3 are performed without act 42.Different coordination acts 32 through 36 may be provided.

In act 30, distance determination is coordinated. Coordination isperformed using wired or wireless transmissions. For example, wirelessradio frequency transmissions and receptions between various componentswithin a network or between any two components for determining adistance are performed.

As represented in act 32, a network of devices including a buildingautomation device within a building is configured for distancedetermination. Radio frequency signals control one or more devices tooperate in a distance determination mode. Alternatively, the type ofdistance determination received signal triggers operation for distancedetermination.

In act 34, a test signal for determining distance is generated. The testsignal is generated from a particular device, but may be transmittedfrom a plurality of devices in other embodiments. For example, anacoustic test signal is generated from one device within a network ofdevices in response to control signals from a radio frequencytransmission.

In act 36, other devices within the network are poled to determine whichdevices adequately received the test signal. A group of buildingautomation devices is then assigned to determine respective distancesbetween the source of the test signal and each of the devices within thegroup in act 36. By using a test signal and assigning certain devicesfor reception of information from the test signals, devices associatedwith reception only through a long time-of-flight associated with one ormore echoes, devices spaced too far from a device to give reliableinformation or devices separated by interfering structures, such aswalls, may be eliminated from the distance determination associated witha given device to avoid erroneous information due to the buildingenvironment. In alternative embodiments, a test signal is nottransmitted. In yet other embodiments, a plurality of test signals aretransmitted with the same or different signal strength or othercharacteristics. Use of test signals or other signals and sufficientreception by various devices may provide distance information withoutfurther measurement of an actual distance. For example, reception of atest signal with a certain amount of signal strength may indicateproximity of the source of the signal as being within a same room as thereceiving device.

After any configuration or coordination between devices within anetwork, a distance determination is performed. Where a given device hasmore than one other device assigned for distance determination, two ormore distances are determined from the two or more other devices. Thedifferent distances may be generated in response to a same initial orsource transmission or different transmissions. For example, asequential assignment or time slots are assigned for each of thedifferent distances and corresponding devices, or coding is used toidentify one signal as being for a particular device rather than otherdevices.

In act 38, a signal is wirelessly transmitted from a building automationdevice within a building. For example, a radio frequency or acousticsignal is transmitted. For an acoustic signal, an ultrasound signal istransmitted. Alternatively, an audible signal is transmitted. Bothacoustic and radio frequency signals may be transmitted at a same ordifferent times for use in determining distance. A transmitted signalincludes coding or other information, such as indicating a time oftransmission. Alternatively, the signal is free of additional coding ortime of transmission coding. In one embodiment, the signal is asinusoidal, bipolar or other signal type. In another embodiment, thesignal includes data, such as associated with coding, and the data isused to identify a time, start a timer or start a counter.

In act 40, the transmitted signal is received. For example, an acousticor radio frequency signal is received. The reception occurs within thebuilding, such as by a building automation device or other device. Thedesired signal is distinguished by other signals, such as echoes ornoise, by a strength and/or a timing of the signal. For example, a firstto be received or first to arrive signal with sufficient signal strengthis identified as a signal of interest or the signal least likely to beassociated with noise or an undesirable number of echoes. Subsequentsignals within a given time period are rejected. Alternatively,subsequent signals within the time period are accepted and used toindicate or identify possible structures or other sources ofinterference.

The timing of receipt of the signal is based on identifying acharacteristic of the signal. In one embodiment, a data marker isidentified. For example, a frame marker, such as a marker provided inevery or some frames pursuant to a protocol, is detected. Othercharacteristics may be detected. The detection identifies a time ofreceipt of the signal. The time of receipt is used to determine atime-of-flight, time difference or to trigger a timer or counter.

Where one-way distance determination is performed, the time-of-flightfrom the transmission of the signal to the reception of the signal isused with the rate of propagation of the signal to determine a distance.The clocks of the transmission device and the reception device aresynchronized to provide accurate relative timing. Alternatively, theclocks are unsynchronized but have sufficiently accurate time stampcapabilities to determine the distance within a sufficiently desiredrange of accuracy, such as within inches, feet or meters. By accountingfor any drift from a master clock, the distance may be determined.

To avoid synchronization issues, a two-way distance determinationcommunication is provided. Alternatively, two-way distance determinationcommunication is provided even with synchronized devices. In act 42, thebuilding automation device or other device receiving an originallytransmitted signal inserts a set time delay between the reception of asignal and subsequent transmission of another signal. The set time delayis inserted by delaying transmission of a subsequent signal by a programor predetermined amount of time after reception of the original signal.For increased accuracy, a portion of the receive signal is identified,such as a first zero crossing. The inserted time period begins based onthe reception of the identified portion and ends by transmission of asignal or a transmission of a specific portion of the signal, such as afirst zero crossing. The time delay is inserted by a countdown timer ora counter of clock cycles, data or other periodic event.

In another embodiment, a delay interval from detected receipt isintroduced without a countdown timer. For example, a counter (e.g.,clock cycle counter) reaching a particular value causes transmission ofa return signal after an interval. As another example, other timed ornon-timed operations are used to provide the interval. A communicationsprotocol may establish a response time, such as an immediate responsetime, for communications. By using an immediate or established responsetime for transmitting the signal, a known or determinable delay intervalis provided. The interval may be determined with or without additionalcounters or delay timers. Rather than counters or timers, a time stampor difference in time may be used.

In act 44, a responsive signal is transmitted after the interval orinsertion of the delay. The responsive transmitted signal has a same ordifferent format at the original signal transmitted in act 38.Additional, different or no coding may be provided. The timing of theresponsive signal may be based on detection of data, modulation of data,or other event. The same or different communications medium, such asacoustic versus radio frequency, is used for the subsequenttransmission.

In act 48, the subsequently transmitted signal is received by theoriginating device. The reception and detection is performed similar ordifferently than the act 40.

The distance of interest is between two different devices. The sourcedevice performing acts 38 and 46, the remote or destination deviceperforming acts 40 and 44 or a different, remote device receives thetiming information and determines the distance. From the perspective ofthe source device, a transmission is the initial step followed byreception of a responsive signal. From the perspective of the responsiveor intermediate device, reception of the signal in act 40 is the initialstep and proceeds through to transmission of the responsive signal inact 44.

In one embodiment, the transmission and reception of signals areperformed in a well distributed manner, such as from point sources.Alternatively, directional transmission or reception may be provided.For example, an omni directional signal is generated. The reception isperformed with an array, allowing identification of a direction of theomni directional transmission by differences in time-of-flight to eachelement of the array. Subsequent transmission is focused along a beam orin a general direction back towards the source. For any subsequentdistance measurements, the original source may transmit and receive in agiven direction based on information provided about the direction of theresponsive or intermediate device.

In act 48, the distance associated with the building automation deviceis determined. The distance is determined as a function of thetime-of-flight for one or more signals, the set time delay or interval,or combinations thereof. The time-of-flight information is determined bysubtracting a time of transmission from a time of reception.Alternatively, the time of reception determines the time-of-flight wherethe time of transmission is assigned as a zero time. Differences in timeor sequences of counts may be used.

Any portion of the transmitted signal may be used for identifying thetime-of-flight, such as determining a time of propagation of the signalfrom a first zero crossing after the first half cycle to reception ofthe first zero crossing. Where a delay time is inserted, the processoris provided with the set delay time as part of the signal, as part ofthe communication in parallel to or in a different path than the signalor as previously programmed and set for various devices. The insertedtime period is subtracted from the two way time-of-flight time toidentify an actual time-of-flight to and from a device.

In another example, the time-of-flight is determined from data detectionevents. A message of any length, such as a 15-20 symbol message, istransmitted from the source device. Particular data in or part of themessage is detected in the source device or used for starting a count ortime-stamp. The destination device receives the data and detectsparticular data to identify that the message is associated with distancedetermination. Alternatively, the destination device is configured tooperate for distance determination without detecting particular data.The destination device responds after a particular interval, such as animmediate response defined by protocol of 8 or other number of symbols.A counter on the destination device counting from data detection onreceipt to data detection on transmit to a response signal is sent backto the source device. The source device detects the received responsesignal, such as identifying particular data. The counter of the sourcedevice ceases counting or the time is noted. The distance is determinedby removing the interval for response by the destination device from theinterval response of the source node and dividing by two. For example,the time-of-flight may correspond to two symbols after removing the 8symbol interval. The two symbols, count, time difference or otherinformation corresponds to a distance.

In an embodiment determining the time-of-flight using acousticinformation, the distance is determined from a speaker to a microphoneas a function of one or more acoustic signals. For a two-way response,the distance is determined as a function of time-of-flight for twoacoustic signals. A second acoustic signal is transmitted from adifferent speaker co-located with a microphone. In response to a firstsignal being received at the microphone, the second signal istransmitted from a speaker after a set time delay. The second acousticsignal is then received at a microphone co-located with the speaker ofthe source or original signal. The time from transmission of the sourcesignal to reception of the responsive signal minus a set time delayindicates a two way time-of-flight. By multiplying the value by thespeed of sound and dividing by two, a distance is provided between thetwo devices. For a frequency embodiment, a similar process is performed.

While the invention has been described above by reference to variousembodiments, it should be understood that many changes and modificationscan be made without departing from the scope of the invention. It istherefore intended that the foregoing detailed description be regardedas illustrative rather than limiting, and that it be understood that itis the following claims, including all equivalents, that are intended todefine the spirit and scope of this invention.

1. A method for determining a distance for a building automation device,the method comprising: (a) wirelessly transmitting a first signal fromthe building automation device within a building; (b) wirelesslyreceiving a second signal at the building automation device within thebuilding; and (c) determining a distance associated with the buildingautomation device as a function of a time-of-flight for the first andsecond signals and a known time delay interval.
 2. The method of claim 1wherein (b) is performed after (a), and wherein a remote buildingautomation device within the building responds to the first signal afterthe delay interval, the response being the second signal.
 3. The methodof claim 1 wherein (c) comprises determining the distance as a functionof the delay interval being an immediate response time.
 4. The method ofclaim 3 wherein the immediate response time is set by a communicationsprotocol.
 5. The method of claim 1 wherein (c) comprises determining thedistance as a function of the delay interval comprising a clock cyclecount.
 6. The method of claim 1 wherein (c) comprises determining thedistance as a function of the delay interval comprising a timercountdown.
 7. The method of claim 1 wherein (a) is performed after (b),and wherein the building automation device delays sending the firstsignal by the delay interval after receiving the second signal.
 8. Themethod of claim 1 wherein (c) comprises determining the distance with aprocessor of the building automation device.
 9. The method of claim 1wherein (c) comprises: identifying a data marker in a data stream of thefirst signal, second signal, or first and second signals; anddetermining the time-of-flight as a function of timing of theidentifying data marker.
 10. The method of claim 9 wherein identifyingthe data marker comprises identifying a frame marker.
 11. The method ofclaim 9 wherein identifying the data marker comprises identifying amarker placed in every frame pursuant to a protocol.
 12. A system fordetermining a distance for building automation components, the systemcomprising: a first building automation device having a first wirelesstransmitter, a first wireless receiver and a first processor; a secondbuilding automation device having a second wireless transmitter, asecond wireless receiver and a second processor; wherein the firstwireless transmitter is operable to transmit a first signal, the secondwireless receiver is operable to receive the first signal, the secondwireless transmitter is operable to transmit a second signal in responseto reception of the first signal and after an interval, the firstwireless receiver operable to receive the second signal, and the firstprocessor, second processor or a third processor operable to determine adistance between the first and second building automation devices as afunction of the time from transmission of the first signal to receptionof the second signal.
 13. The system of claim 12 wherein the secondwireless transmitter is operable to transmit the second signal after theinterval associated with an immediate response.
 14. The system of claim13 wherein the interval associated with the immediate response is set bya communications protocol.
 15. The system of claim 12 wherein the secondbuilding automation device is operable to count clock cycles fromreception of the first signal, the interval corresponding to the count.16. The system of claim 12 wherein the second building automation deviceis operable to set a count-down time from reception of the first signal,the interval corresponding to the count-down time.
 17. The system ofclaim 12 wherein the first processor is operable to determine thedistance.
 18. The system of claim 12 wherein the first and secondbuilding automation devices are operable to identify a data marker in adata stream of the second and first signals, respectively; wherein thedistance is a function of timing of the identification.
 19. The systemof claim 18 wherein the data marker comprises a frame marker.
 20. Thesystem of claim 18 wherein the data marker comprises a marker placed inevery frame pursuant to a protocol.
 21. The system of claim 12 whereinthe first and second transmitters comprise speakers and the first andsecond receivers comprise microphones.
 22. The system of claim 12wherein the first transmitter and first receiver comprise a first radiofrequency transceiver, and the second transmitter and second receivercomprises a second radio frequency transceiver.
 23. A method fordetermining a distance for a building automation device, the methodcomprising: measuring a first time from a first data marker in a firstdata packet transmitted from a first device until a second data markerin a second data packet received from a second device; measuring asecond time from the receipt of the first data marker in the seconddevice to the sending of the second data marker in the second packettransmitted from the second device; determining a time-of-flight as afunction of subtracting the second time from the first time and dividingthe result by two.